Which Pokémon pair began the franchise’s second generation of main-series games?

Pokémon Gold and Silver began the franchise’s second generation of main-series games.

The pair was released in Japan in 1999 for the Game Boy Color. It added a new region, Johto, along with new Pokémon, moves, types, characters, and gameplay systems.

Gold and Silver also introduced a real-time day-and-night cycle, breeding, held items, Pokémon genders, and the Dark and Steel types. After completing the Johto adventure, players could return to the earlier Kanto region, making the games unusually expansive for the series.

The games were released in Australia and North America in October 2000 and in Europe in April 2001. Their follow-up, Pokémon Crystal, added further features but did not start a new generation. Generation Two therefore refers specifically to the Gold and Silver era and its enhanced version.